INFLUENCE OF CRYSTALLOGRAPHY UPON CRITICAL NUCLEUS SHAPES AND KINETICS OF HOMOGENEOUS FCC-FCC NUCLEATION .3. THE INFLUENCE OF ELASTIC STRAIN-ENERGY

The influence of crystallography on critical nucleus shapes and kinetics of homogeneous f. c. c. -f. c. c. nucleation was studied by combining the discrete lattice point non-classical model with the microscopic theory of strain energy as applied by Cook and de Fontaine to compositional fluctuations in cubic lattices. The model is applied to f. c. c. nuclei in Al-Cu and Cu-Co alloys. Nuclei in Al-Cu are plates because coherency strain energy predominates. In Cu-Co alloys, the misfit is smaller and the distortion tensor is cubic; thus the nuclei are essentially spherical. Despite this lesser effect, the influence of strain energy on the nucleation kinetics of Co-rich precipitates in a Cu-rich Cu-Co alloy is important, reducing these kinetics by as much as five orders of magnitude.